Various embodiments of the present invention relate to a motor driven system in a vehicle and more particularly, a method and apparatus for preventing undesired movement of the motor driven system.
Some vehicles are provided with motorized windows or sunroofs that move between a closed position and an open position via a motor driven system. When the motor driven system is de-energized and a force is applied to the window or sunroof operatively coupled to the motor and the motor is allowed to be back driven or driven by the applied force, the window or sunroof may be moved from a closed position into at least a partially open position.
Accordingly, it is desirable to provide an apparatus and method for detecting and preventing movement of a motor in a device or system. Typically, the problem is solved by combining the use of relay powered motors and a reduced efficiency of a worm and wheel gear reduction, thus creating the desired degree of drive motor irreversibility. When the motor driven system is de-energized, the relay links motor windings to ground, thus creating a resistive torque that brakes the motor or prevents rotation thereof. The use of relays does not allow controlling the motor speed but only its direction. The demand for speed controlled motion is increasing because it provides a smooth movement and the possibility of reduced speed approaching the travel end, the end user's feedback is positive. Moreover, relays require space and their price is increasing. These drawbacks are solved by an alternative technology called solid-state-relay, which is made of a bridge of MOSFET power transistor. Yet, in the de-energized state, the MOSFET driven motor windings are not short-circuited to ground. The result is that we are losing the contribution of electrical brake effect for irreversibility performance and the problem to be solved is how to recover the desired degree of irreversibility without acting on the second parameter, i.e. decreasing more the efficiency of the worm and wheel gear.